To compare with a regular illuminating light, the light emitting diode has the advantages of being electricity-saving, recyclable and having longer lifetime. With the enhanced brightness and reduced cost, to illuminate by a semiconductor is achievable in the future.
At the present time, the colors of the light emitting diode within the scope of the visible light include red, orange, orangish red, yellow, yellowish green, green, blue and purple. The lack of other optional mixed colors makes the development of light emitting diodes with different wavelengths become one of the focused researches. The traditional method of manufacturing light sources of mixed colors requires light emitting LED chip of more than two colors to be sealed together. The involved die-attachment and bonding procedures during the sealing are quite complicated. Furthermore, since the materials of the light emitting LED chip of two different colors are different, the required driving electric pressures vary as well. Therefore, one of the shortcomings thereof is that it is necessary to add different driving electric currents to adjust the brightness and colors.
A new technique using one light emitting diode to produce multiple colors mainly coats a layer of fluorescent powder on the surface of a LED chip such that the light emitted by the light emitting LED chip excites the layer of fluorescent powder thereby producing another kind of color light and further produces new colors of more wavelengths with the color light from the original light emitting LED chip. For example, the patent of a white light emitting diode (U.S. Pat. No. 5,998,925) of Nichia corporation adds the yellow (YAG) fluorescent powder to a blue light emitting diode with a wavelength about 460 nm and uses the blue light to excite the yellow (YAG) fluorescent powder to emit a yellow light with a longer wavelength about 560 nm. As indicated in FIGS. 2 and 3, the peak of the excitation spectrum or the absorption spectrum is at 460 nm approximately. The blue light of this wavelength is able to excite the yellow light with a spectrum about 560 nm from the YAG fluorescent powder. Therefore, a white light emitting diode is generated through the complementary principle of the yellow and the blue colors.
The inventor of the present invention has been granted with many LED related patents in the past years. More especially, the inventor pioneered in utilizing the ultraviolet light to excite the fluorescent powder to produce a white light or various color lights with three wavelengths, for example, U.S. Pat. No. 5,952,681 and U.S. Pat. No. 5,962,971 and the other patents in the process of application.
The present invention of a purplish pink light emitting diode utilizes the abovementioned principle to make a light emitting LED chip excite a fluorescent powder with the difference of using a red fluorescent powder. The excitation spectrums (the absorption spectrum) indicated in FIGS. 4 and 5 show that the components of the red fluorescent powder (1) are 6MgO.As2O5: Mn in FIG. 4 and the components of the red fluorescent powder (2) are 3.5MgO.0.5MgF2.GeO2: Mn. The fluorescent powder used in the present invention is an inorganic oxide with an excitation peak at about 420 nm. The purple light emitting diode with a wavelength ranging from 405 to 430 nm irradiates on the fluorescent powder and the purple light excites the red fluorescent powder to produce a red light with a wavelength of 650 nm and the red light further mixes with the purple light generated from the original light emitting LED chip to produce a purplish pink or pinkish red light emitting diode.
To enable a further understanding of the manufacturing method and contents of the purplish pink light emitting diode of the present invention, the brief description of the drawings below is followed by the detailed description of the preferred embodiment.